310 THE CIRCULATION IN THE BLOOD-VESSELS [CH. XXlt. 



or of a nerve, on any organ, to record its volume changes by the 

 plethysmographic method. Thus, the salivary glands, lobes of the 



FIG. 270. Diagram of Roy's Oncometer. a represents the kidney enclosed in a metal box, which opens 

 by hinge /; b, the renal vessels and duct. Surrounding the kidney are two chambers formed by 

 membranes, the edges of which are firmly fixed by being clamped between the outside metal capsule, 

 and one (not represented in the figure) inside, the two being firmly screwed together by screws at h, 

 and below. The membranous chamber below is filled with a varying amount of warm oil, according 

 to the size of the kidney experimented with, through the opening, then closed with the plug i. 

 After the kidney has been enclosed in the capsule, the membranous chamber above is filled with 

 warm oil through the tube e, which is then closed by a tap (not represented in the diagram) ; the 

 tube d communicates with a recording apparatus, and any alteration in the volume of the kidney 

 is communicated by the oil in the tube to the chamber d of the Oncograph, fig. 271. 



FIG. 271 Roy's Oncograph, or apparatus for recording alterations in the volume of the kidney, etc., 

 as shown by the oncometer a, upright, supporting recording lever I, which is raised or lowered by 

 needle b, which works through/, and which is attached to the piston e, working in the chamber d, 

 with which the tube from the oncometer communicates. The oil is prevented from being squeezed 

 out as the piston descends by a membrane, which is clamped between the ring-shaped surfaces of 

 cylinder by the screw i working upwards ; the tube li is for filling the instrument. 



liver or lung, the limbs, the kidney, spleen, a coil of intestine, etc., 

 can each be easily enclosed in an appropriately shaped gutta-percha 



